Graded midplane

ABSTRACT

An electronic module includes, a circuit board having front and rear edges, and first and second connectors. The rear edge includes, (i) a first section at a first distance from the front edge, and (ii) a second section at a second distance from the front edge, different from the first distance. The first and second connectors are mounted along the rear edge at the first and second sections, respectively, and are configured to connect the circuit board to an interconnect unit.

FIELD OF THE INVENTION

The present invention relates generally to communication equipment, andparticularly to methods and systems for signal interconnection incommunication systems.

BACKGROUND OF THE INVENTION

Electrical connector assemblies used within elements of communicationsystems, such as a midplane of a network switch, are designed withvarious connectivity schemes.

For example, U.S. Pat. No. 6,267,628, whose disclosure is incorporatedherein by reference, describes a high frequency, modular electricalconnector assembly that includes contact/terminal members arranged toreduce crosstalk during use. The connector assembly includes adielectric housing having a receptacle and an insert assembly arrangedtherein.

U.S. Pat. No. 9,118,144, whose disclosure is incorporated herein byreference, describes an electrical connector for connecting bus lines toa card such as a memory card or media card, including a multi-levelconnector comprising a latching device having a plurality of insertablelatch positions that advantageously allows for selectively connecting orisolating an electrical path to an adjoining connector.

U.S. Pat. No. 9,166,312, whose disclosure is incorporated herein byreference, describes a printed circuit board (PCB) assembly for use withfirst and second cables terminated with first and second cable lugs,respectively, each of the first and second cable lugs includes two lugholes defined therein, the includes a PCB and a terminal block.

SUMMARY OF THE INVENTION

An embodiment of the present invention that is described herein providesan electronic module that includes, a circuit board having front andrear edges, and first and second connectors. The rear edge includes, (i)a first section at a first distance from the front edge, and (ii) asecond section at a second distance from the front edge, different fromthe first distance. The first and second connectors are mounted alongthe rear edge at the first and second sections, respectively, and areconfigured to connect the circuit board to an interconnect unit.

In some embodiments, the circuit board has an Integrated Circuit (IC)mounted thereon, and includes circuit traces that connect the IC to thefirst and second connectors. In other embodiments, the IC is equidistantfrom the first and second connectors.

In an embodiment, the rear edge includes a third section located at thesecond distance from the front edge. In another embodiment, the frontedge includes a flat section.

There is additionally provided, in accordance with an embodiment of thepresent invention, an electronic rack that includes, a firstinterconnect unit and a second interconnect unit that includes, a firstsection at a first distance from the first interconnect unit and asecond section at a second distance from the first interconnect unit,different from the first distance, and first and second connectors,which are mounted along the second interconnect unit at the first andsecond sections, respectively, and are configured to connect the secondinterconnect unit to one or more electronic modules inserted into thesecond interconnect unit.

There is additionally provided, in accordance with an embodiment of thepresent invention, a method for producing an electronic module, themethod includes, providing a circuit board having front and rear edges,the rear edge includes, (i) a first section at a first distance from thefront edge and (ii) a second section at a second distance from the frontedge, different from the first distance. First and second connectors areattached to the circuit board along the rear edge at the first andsecond sections, respectively.

There is further provided, in accordance with an embodiment of thepresent invention, an electronic module that includes, a circuit boardhaving front and rear edges, first and second connectors, and anintegrated circuit (IC). The rear edge includes, (i) a first section ata first distance from the front edge and (ii) a second section at asecond distance from the front edge, different from the first distance.The first and second connectors are mounted along the rear edge of thecircuit board at the first and second sections, respectively, and areconfigured to connect the circuit board to an interconnect unit. The ICis mounted on the circuit board and its center is positioned at a firstdistance from the first connector and at a second distance from thesecond connector, such that a sum of the first and second distances isminimal among all possible positions of the IC on the circuit board.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that schematically illustrates adirector-class switch, in accordance with an embodiment of the presentinvention;

FIG. 2 is a schematic, pictorial illustration of a director-classswitch, in accordance with an embodiment of the present invention;

FIG. 3 is a schematic, pictorial illustration of a midplane cage used ina director-class switch, in accordance with an embodiment of the presentinvention;

FIG. 4 is a schematic, top view of a midplane of a director-classswitch, in accordance with an embodiment of the present invention; and

FIG. 5 is a schematic, pictorial illustration of a spine of adirector-class switch, in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Network switches, such as director-class switches, are used, forexample, in data centers that support high data rates on an order ofGigaBits per second (GBPS) or even TeraBits per second (TBPS).

Embodiments of the present invention that are described hereinbelowprovide improved techniques for transferring electrical signals in amidplane, which connects between frontplane and backplane modules of adirector-class switch. In some embodiments, the midplane comprisescables, connectors and interconnect units (such as a spine plate and aleaf plate), which connect between electronic boards such as spine andleaf switches. For example, electrical signals are typically routed froma leaf switch to a spine switch via the leaf plate, a cable and thespine plate. Each leaf switch and spine switch typically comprises oneor more Integrated Circuit (IC) devices, and circuit traces that connectthe IC to the respective interconnect unit, via the connectors.

In practice, the high data rate of the signals (e.g., TBPS) makes thesignals prone to poor signal integrity and high attenuation loss. Inparticular, the inventors have found that the signal loss (per unitlength) in cables is five or six times smaller than in circuit traces.

In some embodiments that are described herein, signal loss is reduced byhaving the spine plate (and the rear edge of the spine switches thatplug into the spine plate) have a graded shape comprising at least twosections located at different distances from a front edge of the spineswitch. In an embodiment, the IC is mounted at a minimal distance fromthe connectors of the spine switch and spine plate. This configurationenables routing the signals via a minimal, and optionally uniform,length of circuit traces from the IC mounted on the spine switch to theconnectors, and routing a longer portion of the path length over cable,thus reducing the signal loss. Moreover, the graded structure enablesfitting the spine switch snugly into a respective slot of the spineplate.

The disclosed techniques provide improved data integrity and lowersignal loss in high-bandwidth (e.g., GBPS and TBPS) communicationsystems, and are particularly important in data centers using Ethernetand Infiniband director-class switches.

System Description

FIG. 1 is a block diagram of a director-class switch 100, in accordancewith an embodiment of the present invention. Director-class switch 100comprises multiple leaf switches 32 (each referred to simply as a “leaf”for brevity). Each leaf 32 connects multiple external ports 104 to oneanother and to one or more internal ports 106. External ports 104 areconfigured to connect to external devices (not shown), such as servers,computers, other switches or storage units. In an embodiment, a singleleaf 32 or multiple leaves 32 may be mounted on a respective leaf board118. In the example of FIG. 1, leaf board 118 comprising leaves 32 isinserted into an interconnect unit referred to as a leaf plate 24. Insome cases, a pair of leaves 32 may be mounted on a single leaf board118.

Switch 100 further comprises multiple spine switches 30 (each referredto simply as a “spine” for brevity). Each spine 30 comprises arespective spine switch (not shown) which connects multiple spine ports114 to one another. In some embodiments, spines 30 are inserted into aninterconnect unit referred to as a spine plate 22. Spine 30 and spineplate 22 are depicted in detail in FIGS. 2-5 below.

In some embodiments, switch 100 comprises a midplane 20, which comprisesmultiple cables 26, made from copper or any other suitable material.Alternatively the cables may comprise optical fibers. In someembodiments, cables 26 connect between spines 30 and leaves 32, whichare inserted into spine plate 22 and leaf plate 24, respectively.

Further details on the architecture of switch 100, including cables 26,spines 30, leaves 32 and their ports are described in U.S. Pat. No.9,531,645, whose disclosure is incorporated herein by reference.

FIG. 2 is a schematic, pictorial illustration of a main unit chassis 200of director-class switch 100 (FIG. 1), in accordance with an embodimentof the present invention. In some embodiments, main unit chassis 200comprises multiple electronic racks or fixtures containing multipleshelves, such as a midplane cage 230, a spine basket unit 208 and a leafbasket unit 236. Spine basket unit 208 comprises multiple spine slots202 for receiving spines 30 (shown in FIG. 1). Leaf basket unit 236comprises multiple leaf slots 212 for receiving leaves 32 (not shown inthis figure). In some embodiments, spine basket unit 208 comprisesmultiple sub units 268, which are separately attached to midplane cage230. Alternatively or additionally, leaf basket unit 236 comprisesmultiple sub units 278, which are separately attached to midplane cage230.

In some embodiments, midplane cage 230 comprises spine plate 22, leafplate 24, cables 26 (shown in FIG. 1) connecting therebetween, andoptionally frame plates 232 used for housing midplane 20 shown in FIG.1.

In some embodiments, power cables 288 enter midplane cage 230 through apower slot 286. In an embodiment, a top opening 292 of midplane cage 230is used for passing control wires (not shown) to the leaf and/or spineboards.

In some embodiments, spine plate 22 has a graded shape comprising threesections: two sections 27 and a single section 29. Spine plate 22 isdepicted in detail in FIG. 3 below. As will be shown further below, eachspine 30 has a similarly graded shape comprising three sections, whichplug into the corresponding sections of spine plate 22.

In the context of the present patent application and in the claims, theterm “graded” refers to an edge (of a plate such as spine plate 22, oran electronic module such as spine 30), which comprises two or moresections, each section located at a different distance from a commonplane, such as leaf plate 24. For example, section 29 of spine plateprotrudes into the midplane so that the distance between section 29 andleaf plate 24 is smaller than the distance between sections 27 and plate24.

Improved Connectivity Using a Graded Midplane

FIG. 3 is a schematic, pictorial illustration of midplane cage 230, inaccordance with an embodiment of the present invention. In someembodiments, spine plate 22 comprises multiple spine ports 202 mountedon frame plates 232, stacked vertically relative to one another, or inany other suitable configuration.

In some embodiments, spine plate 22 comprises multiple sub-plates 39attached between frame plates 232 and sub units 268 shown in FIG. 1. Inalternative embodiments, spine plate 22 is made from a single unit.

In the example of FIG. 3, spine plate 22 comprises four sub-plates 39,whereas the upper fifth sub-plate and cables 26 are absent from thedrawing for the sake of clarity, so as to show leaf plate 24, internalports 106 and the shape of spine plate 22.

In an embodiment, spine plate 22 has a graded shape, in which sections29 and 27 are located at different distances relative to leaf plate 24.In the example of FIG. 3, section 29 protrudes toward plate 24, and isthus closer to leaf plate 24 than sections 27. In the example of FIG. 3,each spine 30 is inserted into a respective spine port 202 and isconnected to spine plate 22 using connectors (shown in FIGS. 4 and 5).

In some embodiments, spine 30 has a flat front edge 28 and a graded rearedge, which is compatible to the graded shape of spine plate 22. Duringinsertion, spine 30 fits snugly into the graded shape of spine plate 22.The rear edge of spine 30 comprises multiple sections, such as threesections, as shown in detail in FIGS. 4 and 5 below.

In alternative embodiments, front edge 28 may comprise multiplesections, arranged in a flat configuration or in a graded configuration.

FIG. 4 is a schematic, top view of midplane 20, in accordance with anembodiment of the present invention. In the present example, two leaves32 are connected to leaf plate 24 via circuit traces 49 and connectors46 located at the right and left sides of leaf plate 32. The connectorson the right side, such as 46A and 46M, may serve for example, asinternal ports 106 of FIG. 1 above and are used for connecting leaf 32to leaf plate 24 electrically and mechanically. The connectors on theleft side, such as connectors 46B and 46N, are used for connecting leafplate 24 to cables 26. In an embodiment, a leaf 32A comprises anIntegrated Circuit (IC) 60A, and a leaf 32B comprises an IC 62A.

In some embodiments, connectors 36 are located on the right and leftsides of spine plate 22. The connectors on the right side, such asconnectors 36B and 36H, connect between spine plate 22 and cables 26,and the connectors on the left side, such as 36A and 36K, connect spineplate 22 with spine 30. Each pair of connectors (e.g., 36A-36B, or46A-46B) represents a single port.

For the sake of clarity, the terms “connector” and “sub-connector” inthe present invention are used interchangeably. For example, asub-connector or connector 36A is configured to connect between spineplate 22 and spine 50 (via traces 48), and sub-connector or connector36B is configured to connect between spine plate 22 and a sub-connectoror connector 46B of leaf plate 24 (via a cable 26A).

In some embodiments, all the connectors in switch 100 (e.g., 36, 46) maybe general off-the-shelf connectors, such as Paladin™ 4 pair×10 Columnconnectors (part number C-JP400-50005) produced by Amphenol TCS (Nashua,N.H.), or any other suitable type of connector, which is configured toconnect any suitable number of pairs (e.g., between 1 and 8 pairs) ofinterconnections. In other embodiments, the connectors attached to spine30 and leaf 32 may be off-the-shelf connectors, and the connectors ofspine plate 22 and/or leaf plate 24 may be customized to the plateconfiguration. In yet other embodiments, any suitable combination of theabove configurations, or any other suitable configuration, may be usedin switch 100.

In some embodiments, spine 30 comprises a substrate 31, such as an ICsubstrate or any other suitable printed circuit board (PCB). In anembodiment, one or more ICs, such as a switching IC 50, are mounted onsubstrate 31. In an embodiment, circuit traces 48 are patterned insubstrate 31, and are configured to conduct electrical signals betweenIC 50 and connectors 36. In some embodiments, spine 30 is inserted intoa slot 202 (shown in FIG. 2) of spine plate 22 and is connected theretoby connectors 36, 36A, 36C and 36K mounted on the rear edge of spine 30.

In some embodiments, director-class switch 100 is configured to operateat a rate on the order of GigaBits per second (GBPS) and TeraBits persecond (TBPS). The data traversing switch 100 is processed by multipleleaves 32 and spines 30 of switch 100, in parallel, so as to increasethe overall rate. In the example of FIG. 4, spine 30 may routeelectrical signals from IC 60A mounted on leaf 32A to IC 62B mounted onleaf 32B.

In some embodiments, the signals are transmitted from IC 60A via a routecomprising traces 49, connectors 46A and 46B, and further transmitted,via cable 26A, connectors 36B and 36A and traces 48, into switching IC50 mounted on spine 30. Then, switching IC 50 transmits the signals toIC 62B via a route comprising traces 48, connectors 36K and 36H, a cable26B, connectors 46N and 46M, and traces 49.

The switching configurations described above are simplified and depictedpurely by way of example. In alternative embodiments, other suitableconfigurations, as well as other suitable switching and routingtechniques can also be used in implementing switch 100 and midplane 20.

As noted above, the inventors have found that the signal loss may bereduced significantly by minimizing the length of the traces and byapplying a uniform length of all traces patterned in the spines andleaves. In the example of FIG. 4, the graded shape of spine 30 and theposition of IC 50 mounted thereon, results in a minimal, and optionallyuniform, length among all traces 48, whereas cable 26A is longer thancable 26B. This technique reduces the rate of signal-loss events inspine 30, because the cable length has a negligible impact on signalloss.

In an embodiment, IC 50 is mounted on spine 30 so that a center of IC 50is located at a given distance from each connector among connectors 36,36C, and 36K. Based on the configuration of spine 30, IC 50 is mountedon spine 30 so that a sum of the given distances between the center ofIC 50 and the respective connectors is minimal among all possiblepositions of IC 50 on spine 30. An exemplary configuration of thistechnique in depicted in detail in FIG. 5 below.

FIG. 5 is a schematic, pictorial illustration of spine 30, in accordancewith an embodiment of the present invention. In some embodiments, spine30 comprises multiple connectors, such as connectors 36, 36A and 36K,used for connecting multiple input/output (I/O) connections.

As can be seen in the figure, the rear edge of spine 30 has a gradedshape that matches the shape of spine plate 22. In some embodiments,connectors 36, 36A, 36C and 36K are mounted along sections 52 and 54,which are located at the rear edge of the graded-shaped substrate 31. Inthe example of FIG. 5, the rear edge is graded in the sense thatsections 52 and 54 are located at different distances from front edge28. In FIG. 5, each of sections 52 is located at a distance D1 from edge28, and section 54 is located at a distance D2 from edge 28, wherein D2is longer than D1.

In some embodiments, traces 48, which are typically made from copper orany other suitable material, are patterned on substrate 31, and areconfigured to conduct electrical signals between I/O interfaces of IC 50and connectors 36, 36A, 36C and 36K. In an embodiment, switching IC 50is mounted on substrate 31 so that the input/output (I/O) interfaces ofIC 50 are located at an equidistance from each respective connectoramong connectors 36, 36A, 36C and 36K. The equidistance refers to thelengths of the relevant traces that each typically comprises one or morestraight-line lags.

In this embodiment, all traces 48 connecting between IC 50 and therespective connectors have a minimized length, which is optionallyuniform, so as to reduce the rate of signal-loss events in spine 30.

In other embodiments, the same techniques may be applied to one or moreleaves 32 (e.g., a graded-shaped edge having multiple sections, similarto sections 52 and 54 having connectors 46 mounted thereon, thus forminga minimal, and optionally uniform, length among traces 49, so as toimprove the operational performance of each leaf 32.

During operation, IC 50 typically produces heat. In some embodiments,one or more heat pipes (not shown) may be mounted on spine 30, in closeproximity to or physically attached to IC 50. The heat pipes areconfigured to transfer (e.g., by conduction or convection) the producedheat away from IC 50, e.g., to a heat sink (not shown).

The examples of FIGS. 1-5 refer to a specific switch configuration. Thisconfiguration, however, is chosen purely for the sake of conceptualclarity. In other embodiments, the spine switch and spine plate may eachcomprise any suitable number of sections. Moreover, the sections of thespine switch and spine plate may be located at different respectivedistances from a common plane, such as the front edge of the spineswitch. In alternative embodiments, the disclosed techniques can beused, mutatis mutandis, in various other types of electronic systems,such as various types of switches. For example, spine 30 may comprisethree or more sections, e.g., at least one section in addition tosections 52 and 54 depicted in FIG. 5, and two or more switching ICs 50.In this embodiment, the shape of the rear end of spine 30, as well asthe pattern of traces 48, and possibly the number of connectors may bechosen for optimal operational performance (e.g., signal-loss rate) ofspine 30.

Moreover, the use of the graded shapes described herein is not limitedto spine switches or to switches in general, and can be used in anyother suitable electronic module. In the present context, spine 30 isregarded as an example of an electronic module, which has a graded edgein order to reduce the lengths of circuit traces.

It will be appreciated that the embodiments described above are cited byway of example, and that the present invention is not limited to whathas been particularly shown and described hereinabove. Rather, the scopeof the present invention includes both combinations and sub-combinationsof the various features described hereinabove, as well as variations andmodifications thereof which would occur to persons skilled in the artupon reading the foregoing description and which are not disclosed inthe prior art. Documents incorporated by reference in the present patentapplication are to be considered an integral part of the applicationexcept that to the extent any terms are defined in these incorporateddocuments in a manner that conflicts with the definitions madeexplicitly or implicitly in the present specification, only thedefinitions in the present specification should be considered.

The invention claimed is:
 1. An electronic module, comprising: a circuitboard having front and rear edges, wherein the rear edge comprises (i) afirst section at a first distance from the front edge and (ii) a secondsection at a second distance from the front edge, larger than the firstdistance; first and second connectors, which are mounted along the rearedge at the first and second sections, respectively, and are configuredto connect the circuit board to an interconnect unit by connecting,respectively, to first and second different connectors of theinterconnect unit; and an Integrated Circuit (IC) mounted on the circuitboard, and comprises circuit traces that connect the IC to the first andsecond connectors, such that at least a portion of the IC is located ata third distance from the front edge, larger than the first distance. 2.The electronic module according to claim 1, wherein the IC isequidistant from the first and second connectors.
 3. The electronicmodule according to claim 1, wherein the rear edge comprises a thirdsection located at the second distance from the front edge.
 4. Theelectronic module according to claim 1, wherein the front edge comprisesa flat section.
 5. An electronic rack, comprising: a first interconnectunit; and a second interconnect unit shaped as a graded planar plate,comprising: a first section at a first distance from the firstinterconnect unit and a second section at a second distance from thefirst interconnect unit, larger than the first distance, wherein thefirst and second sections are located on the graded planar plate; andfirst and second connectors, which are mounted along the secondinterconnect unit at the first and second sections, respectively, andare configured to connect the second interconnect unit to one or moreelectronic modules inserted into the second interconnect unit.
 6. Theelectronic rack according to claim 5, wherein the first interconnectunit is flat.
 7. The electronic rack according to claim 5, wherein thefirst interconnect unit comprises multiple third connectors, which areconfigured to connect the first interconnect unit to the secondinterconnect unit.
 8. The electronic rack according to claim 7, whereinat least one of the first and second connectors comprises a firstsub-connector, which is configured to connect between the secondinterconnect unit and the electronic module, and a second sub-connector,which is configured to connect between the second interconnect unit andthe third connector.
 9. The electronic rack according to claim 8, andcomprising a cable, which is configured to connect between the secondsub-connector and the third connector.
 10. A method for producing anelectronic module, the method comprising: providing a circuit boardhaving front and rear edges, wherein the rear edge comprises (i) a firstsection at a first distance from the front edge and (ii) a secondsection at a second distance from the front edge, larger than the firstdistance; attaching to the circuit board first and second connectorsalong the rear edge at the first and second sections, respectively,wherein the first and second connectors connect the circuit board to aninterconnect unit by connecting, respectively, to first and seconddifferent connectors of the interconnect unit; and mounting on thecircuit board an Integrated Circuit (IC), and forming circuit tracesthat connect the IC to the first and second connectors, such that atleast a portion of the IC is located at a third distance from the frontedge, larger than the first distance.
 11. An electronic module,comprising: a circuit board having front and rear edges, wherein therear edge comprises (i) a first section at a first distance from thefront edge and (ii) a second section at a second distance from the frontedge, larger than the first distance; first and second connectors, whichare mounted along the rear edge of the circuit board at the first andsecond sections, respectively, and are configured to connect the circuitboard to an interconnect unit, by connecting, respectively, to first andsecond different connectors of the interconnect unit; and an integratedcircuit (IC), which is mounted on the circuit board, such that at leasta portion of the IC is located at a third distance from the front edge,larger than the first distance, and whose center is positioned at afirst distance from the first connector and at a second distance fromthe second connector, such that a sum of the first and second distancesis minimal among all possible positions of the IC on the circuit board.12. The electronic module according to claim 11, wherein the circuitboard comprises circuit traces that connect the IC to the first andsecond connectors.
 13. The electronic module according to claim 11,wherein the IC is equidistant from the first and second connectors. 14.The electronic module according to claim 11, wherein the rear edgecomprises a third section located at the second distance from the frontedge.
 15. The electronic module according to claim 11, wherein the frontedge comprises a flat section.